*Copay* is an easy-to-use, open-source, multiplatform, multisignature, secure bitcoin wallet platform for both individuals and companies. With Copay, now everyone using bitcoin can enjoy a wallet with corporate-level security!
When friends or company executives join a *Copay* wallet, more than one person must sign every transaction. If your computer is ever compromised and your private keys are stolen, the bitcoins are still safe if you used the multi-signature feature. This feature is in addition to state-of-the-art encrypted storage and communication.
Open test/index.html in your browser to test models. Install [mocha](https://www.npmjs.com/package/mocha) and [karma](https://www.npmjs.com/package/karma-cli) to test the services and controllers.
The default configuration can be found in the config.js file - see [config.js](https://github.com/bitpay/copay/blob/master/config.js) for more info. This configuration could be partially overridden with the options set at the "Settings" tab.
gyp ERR! stack Error: `gyp` failed with exit code: 2
```
This is because Ubuntu 14.04 and 14.10 have Python 2.7 installed by default but **gyp** requires Python 2.6. See: (http://stackoverflow.com/questions/21155922/error-installing-node-gyp-on-ubuntu)
One solution to this issue is to use *Copay* with a Python version manager and install 2.6. For example, if you have pyenv installed:
To install it go to `chrome://extensions/` in your Chrome browser and ensure you have the 'developer mode' option enabled in the settings. Then click on "Load unpacked chrome extension" and choose the directory mentioned above.
*Copay* implements a multisig wallet using [p2sh](https://en.bitcoin.it/wiki/Pay_to_script_hash) addresses. It supports multiple wallet configurations, such as 3-of-5 (3 required signatures from 5 participant peers) or 2-of-3. To create a multisig wallet shared between multiple participants, *Copay* requires the public keys of all the wallet participants. Those public keys are then incorporated into the wallet configuration and combined to generate a payment address where funds can be sent into the wallet. Conversely, each participant manages their own private key and that private key is never transmitted anywhere.
To unlock a payment and spend the wallet's funds, a quorum of participant signatures must be collected and assembled in the transaction. The funds cannot be spent without at least the minimum number of signatures required by the wallet configuration (2 of 3, 3 of 5, 6 of 6, etc). Once a transaction proposal is created, the proposal is distributed among the wallet participants for each to sign the transaction locally. Once the transaction is signed, the last signing participant will broadcast the transaction to the Bitcoin network using a public API (defaults to the [Insight API](https://github.com/bitpay/insight-api)).
*Copay* also implements [BIP32](https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki) to generate new addresses for peers. The public key that each participant contributes to the wallet is a BIP32 extended public key. As additional public keys are needed for wallet operations (to produce new addresses to receive payments into the wallet, for example) new public keys can be derived from the participants' original extended public keys. Once again, it's important to stress that each participant keeps their own private keys locally - private keys are not shared - and are used to sign transaction proposals to make payments from the shared wallet.
For more information regarding how addresses are generated using this procedure, see: [Structure for Deterministic P2SH Multisignature Wallets](https://github.com/maraoz/bips/blob/master/bip-NNNN.mediawiki).
*Copay* peers encrypt and sign each message using the hybrid Elliptic Curve Integrated Encryption Scheme ([ECIES](http://en.wikipedia.org/wiki/Integrated_Encryption_Scheme)).
The *identity key* is an ECDSA public key derived from the participant's extended public key using a specific BIP32 branch. This special public key is never used for Bitcoin address creation and should only be known by members of the WR. In *Copay* this special public key is named *copayerId*. A hash of the copayerId named *peerId* is used to register with a peerjs server. For more information on this hash value, please refer to the Bitcoin Wiki page entitled [Identity protocol v1](https://en.bitcoin.it/wiki/Identity_protocol_v1).
Registering with a hash avoids disclosing the copayerId to parties outside of the WR. Peer discovery is accomplished using only the hashes of the WR members' copayerIds. All members of the WR know the full copayerId's of all the other members of the WR.
Copay uses the powerful and feature-rich [Bitcore](https://github.com/bitpay/bitcore) Javascript library for Bitcoin-related functions. Bitcore should be built this way:
Copay currently supports [BIP70 (Payment Protocol)](https://github.com/bitcoin/bips/blob/master/bip-0070.mediawiki), with the following limitations:
* Only one output is allowed. Payment requests that are more that one output are not supported.
* Only standard Pay-to-pubkeyhash and Pay-to-scripthash scripts are supported (on payment requests). Other script types will cause the entire payment request to be rejected.
* Memos from the custormer to the server are not supported (i.e. there is no place to write messages to the server in the current UX)
